Adjacent signal interference is one of the major sources of noise in digital TV signals. For example, TV signals, including analog and digital signals, occupy certain frequencies in UHF bands. In Europe, each DVB-T/H and PAL/SECAM channel occupies 8 MHz in UHF band. As those having skill in the art know, there is no guard band between these channels. Thus, in some areas, interference TV signals are closer than the desired TV signals, resulting in adjacent interference being present when receiving the desired TV signals. Accordingly, achieving good signal quality in the presence of adjacent interference is a challenging issue in designing DVBT/H receivers.
A common solution for suppressing adjacent interference is adding a low pass filter (LPF) to filter out the interference. However, the quality of the signal going into the LPF determines the final receiver performance. The signal quality before the LPF depends on the tuner, automatic gain control (AGC) and an analog-to-digital converter (AD C). Additionally, some tuners need to be configured differently in order to deal with different adjacent interference, e.g., N±1, N±2, etc.
One solution used for adjacent interference detection is to measure signal power before and after the LPF. If the signal power before the LPF is much larger than the signal power after the LPF, it can be determined that the adjacent interference is present, e.g., for N±1 interference. However, the signal power difference before and after the LPF behaves differently with adjacent interference at different locations with respect to the desired signal, (e.g., N±m, where m>1 interference). Thus, adjacent interference detection, and determining its location are important for adjusting the tuner, the AGC and the ADC to obtain desirable performance.
Therefore, there exists a need for an apparatus and method for detecting adjacent interference and determining its location.